Magneto-optical overwriting methods using erasing pulses, each of which has a higher frequency and narrower width than that of the overwriting pulses

Abstract

A method of overwriting information in a magneto-optical memory medium which includes a simultaneous writing and erasing step of continuously irradiating a written information-carrying area of the recording layer of the memory medium with two different pulses from a single laser beam head in accordance with information to be written, regardless of the presence or absence of written information. A variation includes irradiating the written information-carrying area with an erasing pulse from a laser beam head, regardless of the presence or absence of written information, and the then selectively irradiating the information-erased area with a writing pulse from another laser beam head in accordance with information to be written. According to these methods, it becomes possible to carry out a simple and high-speed overwriting with an increased and stabilized bit positioning accuracy.

What is claimed is: 
     
       1. A method of overwriting information onto a magneto-optical memory medium comprising the steps of: a) providing a magneto-optical memory medium having a substrate and a magneto-optical recording layer having a perpendicular magnetization direction characteristic coated thereon, the magneto-optical recording medium having information tracks each of which carries previously selectively recorded magnetic domains;   b) irradiating pulse light beams in accordance with information to be overwritten from a single optical head onto one information track of the information tracks, a first one of the pulse light beams including a series of pulses having a power sufficient to overwrite recorded magnetic domains and the remaining pulse light beam including a series of pulses having a higher frequency than that of the overwriting pulses and having a power sufficient to erase recorded magnetic domains, each of the erasing pulses having a pulse width narrower than that of the pulse of overwriting pulses; and   c) alternately irradiating the overwriting pulses and the erasing pulses onto the track during overwriting and erasing, respectively.   
     
     
       2. A method according to claim 1, wherein a frequency of said first one of the pulse light beam is 3 times or more higher than a maximum frequency of the remaining pulse light beam. 
     
     
       3. A method according to claim 1, wherein the information is "0" and "1" binary signal information. 
     
     
       4. A method according to claim 1, wherein the height of the pulses of the remaining pulse light beam is lower than a height of the pulses of the first one of the pulse light beams. 
     
     
       5. A method according to claim 1, wherein a height of the pulses of the remaining pulse light beam is the same as the height of the first one of the pulse light beams. 
     
     
       6. A method according to claim 1, wherein overwriting of information is carried out in the presence of an external magnetic field. 
     
     
       7. A method according to claim 1, wherein the magneto-optical memory medium is a disk. 
     
     
       8. A method of overwriting information in a magneto-optical memory medium which comprises a substrate and a magneto-optical recording layer having a perpendicular magnetization direction characteristic coated on the substrate and having information tracks each of which carries previously selectively recorded magnetic domains, said method comprising the steps of: a) irradiating the information tracks with pulse light beams from a single optical head in accordance with information to be overwritten, a first one of the pulse light beams having power sufficient to overwrite recorded magnetic domains and the other ones of the pulse light beams including a series of pulses having a higher frequency than that of the overwriting pulses and having a power sufficient to erase recorded magnetic domains, each of the erasing pulses having a pulse width narrower than that of each of the overwriting pulses; and   b) alternately irradiating the overwriting pulses and erasing pulses onto the information tracks during overwriting and erasing, respectively.   
     
     
       9. A method according to claim 8, wherein overwriting of the information is carried out in the presence of an external magnetic field. 
     
     
       10. A method according to claim 8, wherein the magneto-optical memory medium is a disk.